The trouble came Tuesday when Obama paid tribute to Jan Karski, the former Polish officer who escaped Nazi imprisonment in World War II and provided firsthand accounts to the Western Allies of atrocities. Karski received the award posthumously.

"Before one trip across enemy lines, resistance fighters told him that Jews were being murdered on a massive scale, and smuggled him into the Warsaw Ghetto and a Polish death camp to see for himself. Jan took that information to President Franklin Roosevelt, giving one of the first accounts of the Holocaust and imploring to the world to take action," Obama said.

The president's use of the term "Polish death camp," rather than Nazi death camp sparked outrage in Poland.

Obama's words "touched all Poles," Prime Minister Donald Tusk said in a statement. "We always react in the same way when ignorance, lack of knowledge, bad intentions lead to such a distortion of history, so painful for us here in Poland, in a country which suffered like no other in Europe during World War II.

"We cannot accept such words even if they are spoken by the leader of a friendly power -- or perhaps especially in such situations -- since we expect diligence, care and respect from our friend on issues of such importance as World War II remembrance."

The White House issued a statement from National Security Council spokesman Tommy Vietor on the president's wrong word choice.

"The president misspoke -- he was referring to Nazi death camps in Poland," the statement said. "We regret this misstatement, which should not detract from the clear intention to honor Mr. Karski and those brave citizens who stood on the side of human dignity in the face of tyranny."

White House spokesman Jay Carney echoed that message in comments to reporters Wednesday.

"On several occasions -- including his visit last year to the Warsaw Ghetto memorial, his remarks at the Holocaust Museum just last month and his video message at the 65th anniversary of the liberation of Auschwitz -- President Obama has paid tribute to the terrible loss of innocent Poles in Nazi death camps during the Holocaust.

"Again, we regret the misstatement, but that's what it was."

Polish Foreign Minister Radek Sikorski tweeted Tuesday night: "White House apologizes for outrageous blunder. PM Tusk will take his position in the morning. It's a shame that this important ceremony was overshadowed by ignorance and incompetence."

Tusk said Wednesday the incident could pose an opportunity for the United States "to support Poland in its efforts towards historical truth, towards the correct phrasings, the right assessment of what happened during World War II on Polish territory and throughout Europe. ... When someone says 'Polish death camps,' it is as if there were no Nazis, no German responsibility, as if there was no Hitler -- that is why our Polish sensitivity in these situations is so much more than just simply a feeling of national pride."

Tusk said he is convinced that "our American friends are capable of a stronger reaction ... than just the correction itself and the regret which we heard from the White House spokesperson.

"We take note of these words, but it seems that it would be even more important for the United States than for Poland to end this with class. This is how one acts with regard to tried-and-tested friends, but this is also how one acts in your own, well-defined interest."

Obama has spoken of the bravery of Poles during World War II in past speeches. Last year, he visited the Warsaw Ghetto Memorial honoring those who perished in the Holocaust.

According to the website of the U.S. Holocaust Memorial Museum in Washington DC, at least 1.5 million Polish citizens were sent into forced labor in German territory between 1939 and 1945.

"Hundreds of thousands were also imprisoned in Nazi concentration camps," it says in its Holocaust Encyclopedia.

"It is estimated that the Germans killed at least 1.9 million non-Jewish Polish civilians during World War II. In addition, the Germans murdered at least 3 million Jewish citizens of Poland."